1. Sunspots

2.Arrangements of continents

3.Natural catastrophes – meteorites and volcanoes

4.Earth’s orbit (Milankovitch cycles) –

a) Eccentricity – shape of orbit changes every 100,000 years

b) Tilt – oscillates by 1.5° every 41,000 years

c) Wobble – circles the axis every 23,000 years.

5. Changes in ocean currents

El Niño is an oscillation of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe.

• During El Niño winds across the Pacific change direction and blow from West to East.

• This changes the weather patterns around the Pacific.

• Occurs every 3 – 7 years although they appear to be getting more regular

El Nino happens in this area of the world in the Pacific Ocean

• The trade winds move warm surface water towards the western Pacific

•Cold water wells up along the west coast of South America (near Peru)

•Upwelling important for fish stocks in Peru

• Air pressure over West coast of S. America becomes low and air over west Australia high pressure

• The normal east to west trade winds over pacific are disrupted and warm water ‘sloshes’ eastwards

• No upwelling on South American coast

There are a few theories that surround it’s cause and here are a few.

1.Rossby wave - wave lowers Thermocline in W. Pacific reducing the upwelling of water. Winds then blow towards warmer water and event starts.

Tropical storms

if storms are strong enough they can blow water eastwards and start the event.

Heat from sea floor

by sea floor volcanoes (no evidence)

El Nino the Movie

With the movement of warm water back Eastwards it prevents any upwelling of cold nutrient-rich, water on which Plankton feed. Plankton is the main food of the anchovy which is one of the main fishing types in Peru!

Warm water also expands. So as the water piles back East towards Peru sea levels increase by 30cm!(Thermocline – sharp boundary

between cold deep water and warmer surface water.)

This means the knock on effects around the world

Reduced Hurricane Activity

Hot Summers in Europe Floods in Kenya

and BangladeshDroughts in Brazil Fires

in Indonesia

A third weather condition can arise called La-Nina

Really simple! All it is, is an exaggerated version of normal conditions.

Air pressure is unusually high over the west coast of South America and low over Eastern Australia

As warm water is pushed westwards sea levels rise by up to 1m

Around Indonesia and Philippines. Strong uplift of air leads to heavy Rain!

Global climate La Niña impacts tend to be opposite those of El Niño impacts

El Nino years are characterised by an increase in the amount of natural disasters

They upset the balance around the globe causing distinct changes in climate

We are still unsure what affects climate change will have on these processes